Currently, it is essential to construct huge structures (e.g. high-rise buildings, long-span bridges, giant space structures, huge offshore structures, huge underground structures, etc.) in order to ensure the space required for human activities and the usability of space in proportion to an increase in population in future society.
As the structures in the field of civil engineering and construction become taller and more enormous, they are indispensably required to use lightweight and high strength materials.
Steel bars having 400 to 500 MPa grade yield strength are presently commercially used in the construction of high-rise structures, and such a trend is expected to further accelerate in the future.